The present invention relates to a sewing-machine drive. More particularly this invention concerns such a drive which allows intermittent driving of a sewing machine.
A sewing machine customarily has a needle that is vertically displaceable on a housing through a workpiece. A bobbin arrangement under the workpiece cooperates with the needle to form a row of stitches through the workpiece. Typically the machine has an electric drive motor whose output speed is variable by means of a foot pedal. Thus the sewing machine operator may sit at the machine and control the sewing speed with the foot control.
It is occasionally desirable, for basting operations or the like, to drive the sewing machine intermittently. This is normally done by providing the machine with a hand wheel so that the user may manually crank the needle up and down and sew stitch at a time. Between stitches the workpiece may be moved back and forth so that subsequently removable basting stitches can be placed in the workpiece with the machine. Such a system has the considerable disadvantage that the sewing-machine operator must use one hand to displace the needle up and down and the other hand to position the workpiece. When sewing a large garment or the like it is frequently necessary to guide and hold the workpiece with two hands so that such an operation is impossible.
Sewing machines have been designed which have an automatic drive arrangement that allows the machine to be driven in such a manner that it automatically stops after each stitch. Such devices normally incorporate complicated electromagnetic clutches in the drive along with limit switches so that the cost and complexity of the sewing machine is elevated. Furthermore, the violent stopping and starting of such machines leads to frequent breakdowns. The violent stopping and starting also is often extremly noisy and frequently does not stop the needle in the desirable up position.